The Supreme Court also uses the term as in 2:
Insurgent (Merriam-Webster)
1: a person who revolts against civil authority or an established government; especially: a rebel not recognized as a belligerent
2: one who acts contrary to the policies and decisions of one's own political party
edit: It's like 1984 with the way it's use overseas these days, can be used to cast a shadow here at home.